Miso is known to take a long time to produce. Lately, given the trends toward shorter working hours and increased vacation time, there has been a desire for the development of an efficient method of making miso at the production site. The largest bottleneck in developing an efficient method of production without having to invest in plant and equipment is the fermentation step. Shortening the length of the fermentation step has a large effect on all the operations in that it shortens the production time. Conventional fermentation operations are carried out over an extended period of time at a low temperature so as not to deactivate the koji (Aspergillus oryzae). Because the production process is long, common salt or alcohol is often added to prevent other types of microorganisms from growing during the production process.
Consuming a large amount of salt-containing miso is regarded as one cause of the onset of hypertension. Hence, there exists a desire for miso that contains a reduced amount of salt. Low-salt miso to which alcohol has been added is known for this reason, yet salt-free miso has not seen practical application. Although salt-free miso is good for the health, it leaves something to be desired in terms of taste and flavor (soy flavor) and so has not been to the consumer's liking.